Fabrication And Performance Control Of 2D MoS₂ Photodetector

Two-dimensional transition metal dichalcogenides materials(such as MoS2,WS2,SnS2,NbS2)have excellent optical,electrical,optoelectronic,and mechanical properties.The thickness of the material is 0.1?1 nm,and it has an ideal semiconductor band gap(1.5?2.1 eV)and strong light-matter interaction,becoming an ideal material for the next generation of miniature,high-sensitivity,high-stability,and transparent photodetectors.This paper focuses on the non-destructive transfer of the single-layer MoS2 grown by Chemical vapor deposition method from the sapphire growth substrate to the SiO2/Si,PET,PI device substrate.The influence of the transfer method on the material integrity and the degree of introduction of impurities is analyzed.The photoelectric properties of three types of single-layer MoS2 photodetectors under different conditions;The effects of surface vulcanization treatment,low-temperature oxygen plasma treatment,and carbon nitride quantum dot treatment on the photoresponse,switching ratio,response time and other properties of the single-layer MoS2 thin photodetector are studied.The following main research results have been obtained:(1)The polymethyl methactylate and polydimethylsiloxane(PMMA+PDMS)transfer method is used to realize the transfer of single-layer MoS2 to the hard substrate SiO2/Si and the flexible substrate PET.The one-step method is used to realize the transfer of the single-layer MoS2 to the flexible PI substrate.Successfully fabricated two-dimensional SiO2/Si,PET,PI substrate MoS2 photodetectors.(2)The influence of PMMA+PDMS transfer method on the morphology and structure of single-layer MoS2 material is revealed.Optical morphology,raman spectroscopy,and photoluminescence characterization show that the surface of the single-layer MoS2 material is flat and clean after transfer,the internal structure of the material is not damaged,and the energy band has not changed significantly.(3)The photoelectric characteristics of single-layer MoS2 photodetectors on different substrates are revealed.The photocurrent output of the two-dimensional SiO2/Si,PET,PI substrate single-layer MoS2 photodetector increases with the increase of the bias voltage,showing obvious characteristics of the bias voltage regulation output current and the incident light intensity increases,and the photocurrent output by the device increases with the increase of the bias voltage.The optical responsivity of the two-dimensional SiO2/Si substrate photodetector under 385 nm laser,9 V bias voltage,and lower optical power density of 5 mw/cm2 is 0.04 A/W,and the switching ratio is 103,Tr=6.319 s,Tf=2.844 s,indicating that the device has the ability to detect weak ultraviolet light signals.The maximum light responsivity of the two-dimensional flexible PET substrate MoS2 photodetector is 0.35 A/W,Tr=0.38 s,Tf=0.44 s.The maximum light responsivity of the two-dimensional flexible PI substrate MoS2 photodetector is 0.11 A/W,Tr=0.31 s,Tf=0.1 s.(4)It is found that the three methods of surface vulcanization treatment,low-temperature oxygen plasma treatment,and carbon nitride quantum dot doping will have a significant impact on the photoresponse,response time,switching ratio and other properties of the two-dimensional SiO2/Si substrate photodetector.Compared with the unvulcanized device,the vulcanized device has no obvious hysteresis and tailing in the rising and falling stages.The rise time and fall time of the device are Tr=0.83 s and Tf=0.16 s,which are reduced by 8 Times and 15 times.After the device is treated with low-temperature oxygen plasma,the light responsivity of the device is improved,and the response time of the device is reduced.After the device is modified with carbon nitride quantum dots,the light responsivity of the device under ultraviolet light irradiation is increased.